Light stable bismuth oxychloride and process for preparing same

ABSTRACT

Bismuth oxychloride stabilized against light is obtained by heating the bismuth oxychloride at a temperature in the range of from about 300* to about 800* C. for a period of time sufficient to stabilize the bismuth oxychloride. Light stable bismuth oxychloride in pearlescent form produced by this process is useful in cosmetic products.

United States Paton [1 1 Piper Nov. 4, 1975 LIGHT STABLE BISMUTH OXYCHLORIDE AND PROCESS FOR PREPARING SAME [75] Inventor: Roger D. PiperQDeS Peres, Mo.

[73] Assignee: Mallinckrodt, Inc., St. Louis, Mo.

[22] Filed: Feb. 6, 1974 21 Appl. No.: 440,234

[52] US. Cl 423/472; 423/617 [51] Int. Cl. COIG 29/00; COIB 11/00 [58] Field of Search 423/472, 6l7

[56] References Cited UNITED STATES PATENTS 3/1974 Wetzold 423/617 OTHER PUBLICATIONS J. W. Mellors, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. 9, 1929, pp. 679 and 680, Longmans, Green & Co., New York, Copy in Scient. Lib.

Primary Examiner--Edvi/ard Stern Attorney, Agent, or FirmR. J. Klostermann; L. N. Goodwin V [57] ABSTRACT 7 Claims, No Drawings LIGHT STABLE BISMUTH OXYCHLORIDE AND PROCESS FOR PREPARING SAME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to light stable bismuth oxychloride. In a particular aspect this invention relates to light stable nacreous bismuth oxychloride and to a process for preparing same. In a more particular aspect this invention relates to a process for preparing light stable nacreous bismuth oxychloride by heating the bismuth oxychloride at a temperature in the range of from about 300 to about 800 C.

2. Description of the Prior Art Because it possesses a high index of refraction and is available in pearlescent form, bismuth oxychloride is widely used as a nacreous or pearlescent pigment in cosmetic products such as lipstick, eye shadow, rouge and nail polish. The principal drawback in the use of nacreous bismuth oxychloride in such cosmetic products is that the material tends to lose its characteristic white color and darkens on exposure to light, particularly ultraviolet light. Several procedures have been employed in an attempt to minimize the tendency of bismuth oxychloride to materially darken on exposure to light. One such procedure involves using special and expensive packaging materials for the product which serve to screen out light. Another commonly employed procedure involves the addition of light stabilizing materials to the bismuth oxychloride pigment. Such a procedure and the materials employed therein are described, for example, in US Pat. No. 2,974,053, issued Mar. 7, 1961 to Lawrence Suchow. While the use of additives has proven reasonably successful in serving to stabilize bismuth oxychloride products against light deterioration, the incorporation of such additives in cosmetic products in turn presents additional drawbacks, the principal of which arises from the adulteration of the bismuth oxychloride material. An additional disadvantage, of course, is that such additives are expensive and thereby add to the ultimate cost of the cosmetic product.

SUMMARY OF THE INVENTION It is an object of the present invention to provide nacreous bismuth oxychloride which remains stable even after prolonged exposure to light.

It is a further object of the present invention to provide a process for stabilizing nacreous bismuth oxychloride against light, principally ultraviolet light, without the need for incorporating light stabilizing additives into the bismuth oxychloride material.

Other objects and advantages of the present invention will be apparent from the specification and appended claims.

The present invention resides in the discovery that the stability of bismuth oxychloride is significantly improved by heating bismuth oxychloride at a temperature in the range of from about 300 to about 800 C. for a period of time sufficient to stabilize the bismuth oxychloride against light deterioration but insufficient to cause significant sintering of the bismuth oxychloride. While not being limited to any particular theory it is believed that the process of the present invention is effective in stabilizing plate-like crystals of bismuth oxychloride against light deterioration by Substantially eliminating discontinuities in the fine structure of the 2 crystalline platelets. It has been theorized that small defects or discontinuities in the structure of individual crystalline platelets of bismuth oxychloride act as centers for color formation upon exposure to light.

DETAILED DESCRIPTION The process of the present invention is carried out by heating bismuth oxychloride at a temperature in the range of from about 300 to about 800 C. It is an important factor in carrying out the process of the present invention that the temperature and the time at said temperature be coordinated to obtain optimum light stabilization of the bismuth oxychloride without causing substantial sintering of the product. While in its broad aspects temperatures in. the range of from about 300 to about 800 C. are effectively employed for longer or shorter periods, the process of the present invention is typically carried out at a temperature in the range of from about 400 to about 700 C. for a period of from about 1 to about 24 hours. The preferred temperature and time at said temperature, of course, will vary depending, among other things, on the particular bismuth oxychloride sample to be treated, the amount of said sample,the desired end use and the heating equipment. It ifs-generally preferred in most cases and under most conditions that the heating procedure be carried out for from about 6 to about 12 hours at a temperature in therange of from about 450 to about 550 C. It is also preferred to avoid temperatures above 700 C. because of the tendency of the product to sinter at such temperatures even when shortened heating periods are employed. While temperatures in the range of from about 300 to about 400 C. may be successfully employed such=temperatures are generally considered impractical because of the long heating times required.

The following examples illustrate the effectiveness of the process of the present invention in stabilizing crystalline bismuth oxychloride against light. It is to be understood that the examples are presented for the purpose of illustration only and the invention is not limited to the compositions or methods shown therein.

EXAMPLE 1 A sample of white pearlescent bismuth oxychloride was divided into two approximately equal portions. The first portion was heated in an oven at approximately 600 C. for 1 /2 hours. The portions were spread on a glass plate and approximately one half of each portion was covered to prevent light exposure while the remaining one half of each portion was exposed for 20 hours to light from an ultraviolet lamp. On completion of the 20 hour exposure period the materials were visually examined. :The.observations were as follows:

1. Exposedjheat treated material Color: whiteslight color deterioration observed.

2. Unexposed heat treated material Color: white no color deterioration observed.

3. Exposed material (no heat treatment) Color: dark grey substantial color deterioration observed.

4. Unexposed material (no heat treatment) Color: white no color deterioration observed.

EXAMPLE 2 A. Various samples of pearlescent bismuth oxychloride were treated in accordance with the process of the present invention by heating the samples at tempera tures in the range of 400700 C. for periods of time 3 4 ranging from'2 to 24 hours. The samples were exposed Table Lcominued to light using the test procedure described below. The reflective properties (color) of each sample were mea- Sample Y Y After Expmure Y sured before and after exposure using the measurement 38 97.6 81.5 16.1 procedure described below. 5 Z3 3. 22'; :53 Test Procedure 41 97:9 80:2 17.7 A sample of dry powdered bismuth oxychloride was 2% 32 2 if: :g-g packed into a 3 inch compression sample holder 44 equipped with a quartz lense. The sample was then ex- 45 97.9 46 96.8 82.2 14.6 posed for 18 hours to near ultravlolet radiation by plac- 47 972 81 A ing it six inches from an ultraviolet light source (Gen- 48 98.0 84.5 14.5 era] Electric F-l5T8/BLB Black Light). The sample g 323 32g position and radiant flux from the light source were the 51 3 3:9 same for each sample. 9255 Color Measurement Procedure 15 The reflective properties of bismuth oxychloride are measured using a colorimeter (COLOR-EYE Model T bl 2 LS manufactured by Kollmorgen Corporatlon of Attle- Sample No Initial Y Y After UM Exposure Y boro, Mass). The colorimeter is equipped with an 18 inch reflective integrating sphere and is calibrated with 20 l 1 2 97.7 79.9 17.9 a standard reflecting surface so that the standard gives 3 968 79.8 1m a tristimulus Y value of 1 under illumination from a 4 97.0 84.9 12.1 standard CIE (Commission Internationale de lEclairg 32:; 22:8 3:; age) illuminant-C light source. The tristimulus value Y 7 96.6 86.0 10.6 of each sample is measured before and after light expo- 25 g 32% sure. The tristimulus Y value is a direct measure of the 10 luminous reflectance relative to the standard reflecting 11 9740 33 surface. The greater the change in percent Y the 8g 35:; greater is the color deterioration of the sample. The re- 14 96.2 89.0 7.2 sults are given in Table l. 15 16 97.0 90.8 6.2 B. The procedure of A above was repeated with the exception that the exposure time was 24 hours instead of 18 hours. The results are given in Table 2.

C. The procedure of A above was repeated with the Table 3 exception that none of the samples were treated with Sample m 1 Y After u v, heat in accordance with the process of the present in- Y Exposure Y Exposure Time vention. The results together with the ultraviolet expo- 1 95,1 62.6 32.5 21 ,6 hours sure time are g1ven in Table 3. r I g 38 23:? T bl 1 40 4 91.7 32.7 59.0 4% hours 5 92.8 50.1 42.7 l8 hours Sample No. Initial 7: Y Y After U.V. Exposure Y 6 18 hours 1 97.0 80.0 17.0 2 97.9 86.6 11.3 3 90.8 The effectiveness of the process of the present inveng 83:; 32:8 3:2 45 tion in improving the stability of bismuth oxychloride 6 91.4 85.6 5.8 against deterioration caused by exposure to light is ap- 7 parent from the results of these tests. These results 8 95.7 95.8 19.9 9 935 3g] 43 show that the change 1n Y caused by light exposure 3 gof the bismuth oxychloride treated in accordance with 2:1 the process of the present invention was from 3.0% to 13 95.6 84.8 10.8 19.9% whereas the change in Y of the untreated bis- 32 gig muth oxychloride was from 32.5% to 59.0%. 16 1 Various modifications and equivalents will be appar- 3;; g ent to one skilled in the art and such may be made in 19 1 the process of the present invention without departing 20 96.8 90.3 6.5 from the spirit or scope thereof. It is therefore to be ung: 323' 33". 3'3 derstood that the invention is to be limited only by the 25 97:0 89:1 71 scope of the appended claims. 24 97.0 90.3 6.7 1 claim; i2 323 ii; 12 l. A process for the preparation of ultra violet light 27 97.5 88.7 8.8 stable bismuth oxychloride which comprises heating is 3% 23:3 23 bismuth oxychloride at a temperature in the range of 30 97 1 90,0 6,2 from about 300 C. to about 700 C. for a period of g; 3;? 2;; 32 time sufficient to stabilize the bismuth oxychloride 3 against ultra violet light but insufficient to cause sub- 34 813 I64 stantial s'intering of the bismuth oxychloride, said per- 32 32:3 :gg iod of time being in the range of from about 1 to about -37 97.9 81.3 16.6 24 hours.

2. The process of claim 1 wherein the bismuth oxychloride is nacreous bismuth oxychloride.

3. The process of claim 2 wherein the temperature is in the range of from about 400 to about 700 C.

4. The process of claim 3 wherein the temperature is in the range of from about 450 to 550 C. and the heating time is in the range of from about 6 to about 12 hours.

5. Ultra violet light stable nacreous bismuth oxychloride prepared by the process which comprises heating bismuth oxychloride at a temperature in the range of from about 300 to about 700 C. for a period of time sufficient to stabilize the bismuth oxychloride against ultra violet light but insufficient to cause substantial sintering of the bismuth oxychloride, said period of time being in the range of from about 1 to about 24 hours.

6. A process of claim 1 wherein the temperature is in the range of from about 400 to 700 C.

7. The process of claim 6 wherein the temperature is in the range of from about 450 to about 550 C. and the heating time is in the range of from about 6 to about 

1. A PROCESS FOR THE PREPARATION OF ULTRA VIOLET LIGHT STABLE BISMUTH OXYCHLORIDE WHICH COMPRISES HEATING BISMUTH OXYCHLORIDE AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 300*C. TO ABOUT 700*C. FOR A PERIOD OF TIME SUFFICIENT TO STABILIZE THE BISMUTH OXYCHLORIDE AGAINST ULTRA VIOLET LIGHT INSUFFICIENT TO CAUSE SUBSTANTIAL SINTERING OF THE BISMUTH OXYCHLORIDE, SAID PERIOD OF TIME BEING IN THE RANGE OF FROM ABOUT 1 TO ABOUT 24 HOURS.
 2. The process of claim 1 wherein the bismuth oxychloride is nacreous bismuth oxychloride.
 3. The process of claim 2 wherein the temperature is in the range of from about 400* to about 700* C.
 4. The process of claim 3 wherein the temperature is in the range of from about 450* to 550* C. and the heating time is in the range of from about 6 to about 12 hours.
 5. Ultra violet light stable nacreous bismuth oxychloride prepared by the process which comprises heating bismuth oxychloride at a temperature in the range of from about 300* to about 700* C. for a period of time sufficient to stabilize the bismuth oxychloride against ultra violet light but insufficient to cause substantial sintering of the bismuth oxychloride, said period of time being in the range of from about 1 to about 24 hours.
 6. A process of claim 1 wherein the temperature is in the range of from about 400* to 700* C.
 7. The process of claim 6 wherein the temperature is in the range of from about 450* to about 550* C. and the heating time is in the range of from about 6 to about 12 hours. 